Crofe. r 22 APU. Crofer 22 APU. Crofer 22 APU. Crofer 22 APU. Crofer 22 APU. Crofer 22 APU. ThyssenKrupp VDM. High-temperature alloy

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1 Material Data Sheet No. 446 June 28 Edition High-temperature alloy r 22 APU Crofe A company of ThyssenKrupp Stainless ThyssenKrupp VDM TK

2 2 * * is a high-temperature ferritic stainless steel especially developed for application in solid oxide fuel cells (SOFC). At temperatures up to 9 C (1652 F) a chromium-manganese oxide layer is formed on the surface of which is thermodynamically very stable and possesses high electrical conductivity. The low coefficient of thermal expansion is matched to that of ceramics typically used for hightemperature fuel cells in the range from room temperature to 9 C (1652 F). is characterized by: excellent corrosion resistance at high temperatures in anode gas and cathode gas low rate of chromium vaporization ease of working and processing low coefficient of thermal expansion good electrical conductivity of the oxide layer Designations and standards Country National standard Material designation Spezification Chemical Sheet & Plate Strip Wire composition D W.-Nr X1CrTiLa22 DIN EN USA UNS S44535 ASTM A 24 A 24 Table 1 - Designations and standards. Chemical composition Cr Fe C Mn Si Cu Al S P Ti La min. max bal Table 2 Chemical composition (wt.-%). * ThyssenKrupp VDM GmbH produces (APU = Auxiliary Power Unit) under licence from Forschungszentrum Jülich.

3 3 Physical properties Density 7.7 g/cm lb/in. 3 Melting temperature 151 (Solidus) C (Liquidus) 275 (Solidus) F (Liquidus) Temperature (T) Specific heat Thermal Electrical Modulus of Coefficient of conductivity resistivity elasticity thermal expansion between 2 C/68 F and T C F J Btu W Btu in. µω cm Ω circ mil kn 1 3 ksi kg K Ib F m K ft 2 h F ft 2 K F Table 3 Typical physical properties at room and elevated temperatures. Contact resistance, mω cm coercial 18% Cr alloy (1.4742) pre-oxidation time (La, Sr) CrO3 coercial 24% Cr alloy (1.4762) Figure 1 shows the contact resistance of as a function of time while exposed to air at 8 C. The contact resistance of is an order of magnitude lower than traditional ferritic alloy 446 (1.4762) type stainless steels. This is because forms a protective scale that exhibits good electrical conductivity and no SiO 2 sublayer which shows poor electrical conductivity Fig. 1 Contact resistance of various materials used for SOFC in air at 8 C. (After Quadakkers et al., Forschungszentrum Jülich)

4 4 Mechanical properties.2% Yield strength R p.2 Tensile strength Elongation Hardness R m A 5 HRB MPa ksi MPa ksi % (For information only) * / 25** 7 9 Thickness: * (.1.15 ) / **.38 (.15 ) Table 4 - Minimum mechanical properties in the soft-annealed condition for all product forms at room temperature. Product.2% Yield strength Tensile strength Elongation R p.2 R m A 5 MPa ksi MPa ksi % Sheet & Plate Strip Wire Table 5 - Typical mechanical properties for different product forms at room temperature. Stress, MPa Temperature, F Portevin Le Chatelier effect Elongation, % Stress, MPa C 2 C 4 C 6 C 7 C 8 C Temperature, C Strain, % Fig. 3 - Stress-Strain Curves for at various temperatures. Yield strength, Rp.2 Tensile strength, Rm Elongation, A5 First coercial heat Fig. 2 - Typical short-time mechanical properties of soft annealed 22 plate as a function of temperature. Stress, MPa C 1 Time at rupture, hrs Fig. 4 - Creep-rupture strength of soft annealed from the first coercial heat at 7 C in air.

5 5 Corrosion resistance shows excellent corrosion resistance in atmospheres relevant to SOFC applications up to 9 C. The oxide layer of consists of a fine grained inner scale which is predominantly Cr 2 O 3 and a columnar (Mn, Cr) 3 O 4 spinel outer oxide layer. This outer layer reduces chromia evaporation very effectively as shown in Figure 5. Figures 6 to 9 show the corrosion resistance of in atmospheres relevant to SOFC applications at 8 C and 9 C respectively. Current production restricts the residual element content in comparison to the first coercial heat. This results in a vast improvement of the oxidation behavior as clearly shown in Figures 6 to 9 for several coercial heats (sample thickness ranging from 1.5 to 2 ). For comparison the results of the laboratory heat melted with high-purity prematerials prior to the first coercial heat are also included in Figures 6, 8 and 9. Cr release 1 11 kg/s m Cr5Fe1Y 2 O Cr5Fe1Y 2 O 3 94% Cr + 5% Fe + 1% Y 2 O 3 X1CrAl18 18% Cr + 1% Al Fe2Cr5Al 2% Cr + 5% Al 22% Cr +.6% Mn X1CrAl Fe2Cr5Al C Exposure time, hrs Fig. 5 - Chromium release of several materials at 85 C in humidified synthetic air with 2% H 2 O (2 x 1 3 Pa). (After Hilpert, Gindorf et al., Forschungszentrum Jülich).8.6 Weight change, mg/cm First coercial heat Laboratory heat Different current production heats 8 C Weight change, mg/cm First coercial heat } Different current production heats 8 C Fig. 6 - Mass change during discontinuous oxidation tests (25 h cycles) of a laboratory and coercially produced heats in air at 8 C as a function of time. (After Quadakkers et al., Forschungszentrum Jülich) Fig. 7 - Mass change during discontinuous oxidation tests ( h cycles except for the first coercial heat, where 25 h cycles were used) of coercially produced heats in simulated anode gas (Ar + 4% H 2 + 2% H 2 O) at 8 C as a function of time. (After Quadakkers et al., Forschungszentrum Jülich) Weight change, mg/cm First coercial heat Laboratory heat Different current production heats 9 C Weight change, mg/cm First coercial heat Laboratory heat Different current production heats 8 C Fig. 8 - Mass change during discontinuous oxidation tests ( h cycles) of a laboratory and coercially produced heats in simulated anode gas (Ar + 4% H 2 + 2% H 2 O) at 9 C as a function of time. (After Quadakkers et al., Forschungszentrum Jülich) Fig. 9 - Mass change during discontinuous oxidation tests ( h cycles) of a laboratory and coercially produced heats in simulated carbon containing anode gas (Ar + 4% H 2 + 1% CO + 2% H 2 O) at 8 C as a function of time. (After Quadakkers et al., Forschungszentrum Jülich)

6 6 Weight change, mg/cm C Fig. 1 - Mass change during cyclic oxidation tests in air (cycles of 2 h heating and 15 min. cooling) of samples of varying thickness from a production heat restricted in residual elements. (After Quadakkers et al., Forschungszentrum Jülich) Apart from the restriction in residual elements Figure 1 clearly shows that the thickness of sheet material also has a significant effect on the oxidation resistance of. Applications is used for interconnector plates to seperate individual plates in solid oxide fuel cells (SOFC). Fabrication and heat treament can readily be hot and cold worked and machined. Heat treatment Workpieces must be clean and free from all kinds of contaminants before and during any heating operations. may become embrittled if heated in the presence of contaminants such as sulfur, phosphorus, lead and other low-melting-point metals. Sources of such contaminants include marking and temperature-indicating paints and crayons, lubricating grease, fluids, and fuels. Fuels must be as low in sulfur as possible. Natural gas should contain less than.1 wt.-% sulfur. Fuel oils with a sulfur content not exceeding.5 wt.-% are suitable. Due to their close control of temperature and freedom from contamination, thermal treatments in electric furnaces under vacuum or an inert gas atmosphere are to be preferred. Treatments in an air atmosphere and alternatively in gas-fired furnaces are acceptable though, if contaminants are at low levels so that a neutral or slightly oxidizing furnace atmosphere is attained. A furnace atmosphere fluctuating between oxidizing and reducing must be avoided as well as direct flame impingement on the metal. After cold forming a recrystallization thermal treatment is required. Fig. 11 shows the effect on grain size of 5 % cold formed of such a thermal treatment for various temperatures and time-at-temperature intervals. Grain Korngröße, diameter, µm µm Time, Zeit, Min. min Temperature, Temperatur, C Fig Recrystallization diagram of after 5% cold deformation Descaling and pickling Oxides of and discoloration adjacent to welds are more adherent than on standard stainless steels. Grinding with very fine abrasive belts or discs is recoended. Care should be taken to prevent tarnishing. Before pickling in a nitric/hydroflouric acid mixture, the surface oxide layer must be broken up by abrasive blasting or grinding or by pretreatment in a fused salt bath. Particular attention should be paid to the pickling time and temperature. Welding When welding nickel alloys or stainless steels, the following instructions should be adhered to: Workplace The workplace should be in a separate location, well away from areas where carbon steel fabrication takes place. Maximum cleanliness and avoidance of draughts are paramount. Auxiliaries, clothing Clean fine leather gloves and clean working clothes should be used. Tools and machines Tools used for nickel alloys and stainless steels must not be used for other materials. Brushes should be made of stainless materials. Fabricating and working machinery such as shears, presses or rollers should be fitted with means (felt, cardboard, plastic sheeting) of avoiding contamination of the metal with ferrous particles, which can be pressed into the surface and thus lead to corrosion.

7 7 Cleaning Cleaning of the base metal in the weld area (both sides) and of the filler metal (e. g., welding rod) should be carried out with ACETONE. Trichlorethylene (TRI), perchlorethylene (PER), and carbon tetrachloride (TETRA) must not be used as they are detrimental to health. Edge preparation This should preferably be done by mechanical means by turning, milling or planing; abrasive water jet or plasma cutting is also suitable. However, in the latter case the cut edge (the face to be welded) must be finished off cleanly. Careful grinding without overheating is permitted. Included angle The different physical characteristics of nickel alloys and special stainless steels compared with carbon steel generally manifest themselves in a lower thermal conductivity and a higher rate of thermal expansion. This should be allowed for by means of, among other things, wider root gaps or openings (2.5 ), while larger included angles (6 7 ), as shown in Fig. 12, should be used for individual butt joints owing to the viscous nature of the molten weld metal and to counteract the pronounced shrinkage tendency. approx.2 Straight butt weld Sheet thickness up to 2.5 (<.1 in.) Single-V weld 6-7 Sheet/plate thickness ( in.) - 2 ( -.8 in.) Fig. 12 Edge preparation for welding of. Welding process in thin thicknesses ( 1.5 /.6 in.) can be joined to itself by GTAW (TIG) and plasma arc welding without the use of filler metal. It can also be joined by spot welding or roll-seam welding. For welding, should be in the soft-annealed condition and be free from scale, grease and markings. When welding the root, care should be taken to achieve best-quality root backing (argon 99.99), so that the weld is free from oxides after welding the root. Any heat tint should be removed preferably by brushing with a stainless steel wire brush while the weld metal is still hot. Filler metal For the GTAW (TIG) welding process filler metal with the same composition as the base metal is recoended. Welding parameters and influences (heat input) Care should be taken that the work is performed with a deliberately chosen, low heat input as indicated in Tables 6 and 7 by way of example. Use of the stringer bead technique should be aimed at. Interpass temperature should be kept below 12 C (25 F). The welding parameters should be monitored as a matter of principle. The heat input Q may be calculated as follows: Q = U x I x 6 (kj/cm) v x U = arc voltage, volts I = welding current, amps v = welding speed, cm/min. Consultation with ThyssenKrupp VDM s Welding Laboratory is recoended. Postweld treatment (brushing, pickling and thermal treatments) Brushing with a stainless steel wire brush iediately after welding, i.e., while the metal is still hot, generally results in removal of heat tint and produces the desired surface condition without additional pickling. Pickling, if required or prescribed, however, would generally be the last operation performed on the weldment. Also refer to the information under Descaling and pickling. Neither pre- nor postweld thermal treatments are normally required. Striking the arc The arc should only be struck in the weld area, i. e., on the faces to be welded or on a run-out piece. Striking marks lead to corrosion.

8 8 Sheet/ Welding- Filler metal Welding parameterswelding Shielding gasplasma plate process Root pass Intermediate and speed Type & rate gas thick- diameter speed final passes Type & rate ness I U I U m/min. A V A V cm/min. l/min. l/min. 3. Manual approx. 15 Ar 4.6 GTAW Manual Ar 4.6 GTAW Autom. 1.2 approx. Manual GTAW Ar 4.6 GTAW Autom. 1.2 approx. Manual GTAW 2 22 approx. 25 Ar 4.6 GTAW Hot wire Ar 4.6 GTAW Hot wire 1.2 Manual GTAW Ar 4.6 GTAW Plasma 1.2 approx. approx Ar 4.6 Ar 4.6 arc Plasma 1.2 approx Ar 4.6 Ar 4.6 arc In all gas-shielded welding operations, adequate back shielding using Ar 4.6 must be ensured. Figures are for guidance only and are intended to facilitate setting of the welding machines. Table 6 Welding parameters (guide values). Welding process Heat input per unit length kj/cm GTAW, manual, fully mechanised max. 8 Hot wire GTAW max. 6 Plasma arc max. 1 Table 7 Heat input per unit length (guide values). Technical Publications The following publications concerning may be obtained from ThyssenKrupp VDM GmbH or can be downloaded from R. Hojda, W. Heimann, W.J. Quadakkers: Production - capable materials concept for high-temperature fuel cells; ThyssenKrupp techforum, July 23. R. Hojda: Großserientaugliches Werkstoffkonzept für Brennstoffzellen; SCOPE - Das moderne Industriemagazin, April 24. R. Hojda, W. J. Quadakkers: Improved product ; Reprint RP 1/5 from ThyssenKrupp techforum, July 25. R. Hojda, L. Paul: UNS S44535 alloy development for interconnect applications in solid oxide fuel cells; CORROSION 26, Paper No. 6479, NACE International, Houston, 26. H. Hattendorf: Sulfur Tolerant Anode Material for Solid Oxide Fuel Cells; 27 Fuel Cell Seminar; San Antonio, Texas, October 27. Further publications concerning and solid oxide fuel cells (SOFC) may be obtained from the Forschungszentrum Jülich, Dept. IEF-2, Jülich, Germany.

9 9 Availability is available as sheet & plate, strip, and wire. Sheet & Plate (for cut-to-length availability, refer to strip) Conditions: hot or cold rolled (hr, cr),soft annealed and pickled Thickness hr/cr Width 1) Length 1) < 1.5 cr < 3. cr < 7.5 cr/hr hr ) Other sizes subject to special enquiry Thickness hr/cr Width 1) Length 1).43 - <.6 cr <.12 cr <.3 cr/hr hr 32 1) Other sizes subject to special enquiry Strip 1) Conditions: cold rolled, soft annealed and pickled or bright annealed 2) Thickness Width 3) Coil I.D ) 3 4 > ) > > > > ) ) ) Cut-to-length available in lengths from 25 to 4 2) Maximum thickness: bright annealed - 3 cold rolled only ) Wider widths subject to special enquiry 4) Wider widths up to 73 subject to special enquiry Thickness Width 3) Coil I.D ) > ) > > > > ) ) ) Cut-to-length available in lengths from 1 to 158 in. 2) Maximum thickness: bright annealed -.12 in. cold rolled only -.14 in. 3) Wider widths subject to special enquiry 4) Wider widths up to 29 in. subject to special enquiry Wire Conditions: drawn, bright, thermally treated; drawn, bright, thermally treated, redrawn 1 /4 hard to hard; shaved or ground. Dimensions: drawn wire:.16 1 (.63.4 in.) diameter, on spools, in coils and payoff packs; also available on spiders and special spools. The information contained in this data sheet is based on results of research and development work and data listed in applicable specifications and standards available and in effect at the time of printing. It does not provide any guarantee of particular characteristics or fit. ThyssenKrupp VDM reserves the right to make changes without notice. The data sheet has been compiled to the best knowledge of ThyssenKrupp VDM and is given without any liability on the part of ThyssenKrupp VDM. ThyssenKrupp VDM is only liable according to the terms of the sales contract, and in particular to the General Conditions of Sales in case of any delivery from ThyssenKrupp VDM. As updates of data sheets are not automatically sent out when issued ThyssenKrupp VDM recoends to request the latest edition of required data sheets either by phone , by fax , or by under vdm@thyssenkrupp.com. Current issues of brochures and data sheets are also available in the Internet under June 28 Edition. This edition supersedes material data sheet no. 446, dated June 26.

10 Crofe ThyssenKrupp VDM GmbH Plettenbergerstrasse Werdohl P.O. Box Werdohl Germany Phone: Fax: vdm@thyssenkrupp.com